Electronic data is commonly stored on disks of various types. Disk drives hold and rotate the disk while positioning a mechanism over the disk to read data from it or write data to it. Some conventional disk drives use a "flying" read/write head, or "flying head", to access data stored magnetically on circular or spiral grooves, or tracks, of the data storage disk. Engaging the flying head in a position to access data is referred to as loading the head.
Typically, the flying head is positioned over a track at a certain height to allow data reading or data writing. For example, in magneto-optical (MO) disk drives, data is recorded by positioning a head that includes a magnetic coil in proximity to an MO disk, locally heating the MO disk to lower the coercivity of a layer of magnetic media. When the coercivity of the magnetic media is lowered, the magnetic head applies a magnetic field to reverse the magnetic polarity in the heated area recording data on the MO disk. In such MO disk drives, data is read from the magnetic media of the MO disk by illuminating areas of the MO disk with linearly polarized laser light. The Kerr rotation effect causes the plane of polarization of the illuminating laser beam to be rotated. The direction of rotation depends on the magnetic polarity in the illuminated area of the storage media.
To read data from a MO disk the polarization rotation is determined with a pair of optical detectors in a polarization beam splitter to produce an output data signal.
In one prior art method a flying head is initially loaded onto the surface of a stationary MO disk (i.e., not spinning) and no data access operation is taking place. To access data, the MO disk is rotated such that a thin film of air forms between the MO disk and the flying head. The surface of the flying head that is just above the disk surface is known as the air-bearing surface of the head. When the flying head is suspended above the MO disk in this manner, it can be moved over a desired concentric track of the MO disk to access data stored on that track. This technique is referred to as static loading and unloading (also known as contact start-stop, i.e., CSS). Normally, the MO disk must be stationary when the head is loaded or unloaded.
The aforementioned technique has several disadvantages. First, a section of the disk area must be reserved as a "landing zone", which reduces the area available for data storage. Secondly, a head can crash into the surface of the MO disk under certain conditions. For example, head crash can occur whenever the drive is suddenly bumped or dropped, power is cut off from the drive, a contaminant particle gets trapped under the air-bearing surface of the head, etc. When a head crash occurs, damage to the MO disk is likely, as well as a loss of data, and possibly even catastrophic destruction of the drive itself.
Another disadvantage of static loading/unloading systems is the requirement of extremely smooth, flat, slider and media surfaces. In other words, the integrity of the head/disk interface is of paramount importance in a system that performs static loading/unloading. Moreover, these very smooth, flat surfaces must be maintained over the lifetime of the drive, which ordinarily includes thousands of CSS events. In addition, there is a need to maintain an adequate amount of lubrication on the media surface.
Another past approach involves dynamically loading and unloading the head while the MO disk is spinning. FIG. 1 is a top view of a portion of a disk drive that includes apparatus for dynamic loading and unloading of a magnetic head. A rotatably mounted actuator arm 103 is attached to a suspension 106. A slider body or head 109 is typically mounted via a gimbal to the distal end of suspension 106. It is appreciated that the suspension assembly may be manufactured of a single piece of formed material. Most often, suspension 106 incorporates a bend 105, which imparts a spring force and stiffness to the suspension in a direction perpendicular to the planar surface of MO disk 107. Some suspensions include multiple bends for this same purpose.
The angle of bend 105 required to produce the appropriate spring rate and other characteristics required for a particular disk drive is ordinarily calculated before forming suspension 103. Because the forming process is imprecise, some trial and error adjustment usually is required to produce a suspension assembly having the correct mechanical characteristics (e.g., flying height, stiffness, pitch and roll, etc.). Head 109 is loaded onto the disk surface by sliding a rigid extended tip section 128 down a fixed ramp 101 in a direction shown by arrow 102. Ramp 101 is appropriately sloped so that as the head moves over disk 107, it begins flying at a height (above the disk surface) that is proper for write operations.
FIG. 2 is a side view of the suspension assembly of FIG. 1 (not to scale) showing head 109 attached to the distal end of suspension 106. Bend 105 is located at the proximate end of the suspension, near to a mounting plate 111. Well-known ball swaging techniques are normally used to attach mounting plate to a mounting area 113 of actuator arm 103. Note that when head 109 is loaded onto disk 107 suspension 106 flexes so that the bottom, air-bearing surface 115 of head 109 is just above, and approximately parallel to, the planar surface of disk 107.
The major disadvantage of this type of suspension system is the time and expense required to precisely form a correct bend angle at the end of suspension 106. It is also very time-consuming to test the suspension to confirm that it has the appropriate spring force and other mechanical characteristics.